Hinged articulating spacer system for revision knee arthroplasty

ABSTRACT

A hinged articulating spacer system for revision knee arthroplasty includes a femur rod for a femur, and a tibia rod for a tibia. The tibia rod is hingedly couplable to the femur rod to form a hinged rod assembly. A pre-formed femoral spacer component includes bone cement impregnated with an antibiotic. The pre-formed femoral spacer defines an opening that receives the hinged rod assembly. A pre-formed tibial spacer component includes bone cement impregnated with an antibiotic. The pre-formed tibial spacer defines an opening that receives the hinged rod assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication Ser. No. 62/743,994, filed Oct. 10, 2018, the entirety ofwhich is hereby incorporated by reference.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to a hinged articulating spacersystem for revision knee arthroplasty.

BACKGROUND OF THE DISCLOSURE

Revision total knee arthroplasty (TKA) may be performed when total kneeprosthesis becomes infected, for example. One type of revision TKA isperformed in two operations or stages. In the first operation, as shownin FIG. 1, the knee prosthesis is removed to allow the patient and theinfected joint to be treated with antibiotics over a period of time,e.g., 6 to 12 weeks. An antibiotic-loaded spacer is inserted in thejoint space to maintain a certain amount of joint stability and mobilityafter the infected prosthesis is removed. After eradication of theinfection, a second surgery is performed to implant a revision kneeprosthesis.

There are two types of antibiotic-loaded cement spacers: static andarticulating. Referring to FIG. 2, a static spacer 10 creates atemporary arthrodesis with antibiotic-loaded bone cement (e.g., PMMA)and are typically handmade during surgery. Typically, a rigidintramedullary rod 12 is placed within the femur and tibia to spanacross the joint space. Referring to FIG. 3, an articulating spacer,generally indicated at 20, is typically pre-manufactured or pre-formedas femoral and tibial spacer components 24, 26, respectively,manufactured from antibiotic-loaded bone cement. The spacer components24, 26 are secured to the respective bones using bone cement 28, forexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a conventional surgical procedure ofremoving an infected total knee arthroplasty (TKA) prosthesis.

FIG. 2 is a front elevation of a prior art static spacer and rigid rodimplanted in a knee after removing a TKA prosthesis.

FIG. 3 is a front elevation of a prior art articulating spacer implantedin a knee after removing a TKA prosthesis.

FIG. 4 is a front elevation of an illustrated embodiment of an assembledhinged articulating spacer system for revision knee arthroplastyconstructed according to the teachings of the present disclosure.

FIG. 5 is a left side elevation of the hinged articulating spacer systemin

FIG. 4.

FIG. 6 is an exploded side elevation of a hinged rod assembly of thehinged articulating spacer system, including a femur rod and a tibiarod.

FIG. 7 is an exploded rear elevation of the hinged rod assembly,including an exploded hinge pin removed from the hinged rod assembly.

FIG. 8 is an enlarged, fragmentary exploded perspective of the hingedrod assembly showing the distal and proximal ends of the femur and tibiarods, respectively.

FIG. 9A is an exploded side elevation of another embodiment of hinge pinfor the hinged rod assembly.

FIG. 9B is a side elevation of the assembled hinge pin in FIG. 9A.

FIG. 10 is a front elevation of another embodiment of a hinged rodassembly.

FIG. 11A is a front elevation of a femoral spacer component of anarticulating component assembly of the hinged articulating spacersystem.

FIG. 11B is a left side elevation of the femoral spacer component inFIG. 11A.

FIG. 11C is a top plan view of the femoral spacer component in FIG. 11A.

FIG. 12A is a front elevation of a tibial spacer component of thearticulating component assembly of the hinged articulating spacersystem.

FIG. 12B is a left side elevation of the tibial spacer component in FIG.11A.

FIG. 12C is a top plan view of the tibial spacer component in FIG. 11A.

FIG. 13 is a front elevation of the hinged articulating spacer systemimplanted in a knee after removal of a TKA prosthesis, a superiorsegment of an anterior portion of the femoral spacer component beingbroken off to show underlying bone cement.

FIG. 14 is similar to FIG. 13, except the femoral spacer component isshown in full.

FIG. 15 is a left side elevation of FIG. 14.

FIG. 16A is a front elevation of a knee joint after removal of a TKAprosthesis and insertion of femur and tibia rods into the femur andtibia, respectively.

FIG. 16B is similar to FIG. 16A with femoral and tibial spacercomponents inserted into the joint space.

FIG. 16C is similar to FIG. 16B with the femur and tibia rods hingedlycoupled to one another to assemble the hinged articulating spacer systemand bone cement added within the joint space.

FIG. 17A is a front elevation of another embodiment of a femoral spacercomponent for the hinged articulating spacer system.

FIG. 17B is a side elevation of the femoral spacer component in FIG.17A.

FIG. 17C is a top plan view of the femoral spacer component in FIG. 17A.

FIG. 17D is a rear perspective of the femoral spacer component in FIG.17A.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring to FIGS. 4 and 5, an illustrated embodiment of a hingedarticulating spacer system for revision knee arthroplasty constructedaccording to the teachings of the present disclosure is generallyindicated at reference numeral 100. The hinged articulating spacersystem 100 generally comprises a hinged rod assembly, generallyindicated at 102, and an articulating component assembly, generallyindicated at 104. In FIGS. 4 and 5, the hinged articulating spacersystem 100 is assembled. As explained in more detail below, the hingedarticulating spacer system 100 is suitable for use in two-stage revisionTKA. More specifically, the spacer system 100 is implanted afterremoving the infected knee prosthesis to allow for antibiotic treatmentof the infected jointed space (e.g., 6 to 12 weeks) before performingthe revision TKA. The spacer system 100 allows range of motion of theknee, unlike the static spacer, such as shown in FIG. 2. Further, thespacer system 100 inhibits dislocation of the knee joint, unlike aconventional articulating spacer, such as shown in FIG. 3. It isbelieved the implantation of the spacer system 100 allows for betterweight bearing than the articulating spacer, such that motion, paincontrol and subsequent surgical exposure may be better than theconventional articulating spacer.

Referring to FIGS. 4-8, the hinged rod assembly 102 generally comprisesa femur rod 108, and a tibia rod 110 hingedly coupled to the femur rodat a hinged joint to allow rotational or pivoting motion of the tibiarod relative to the femur rod about a transverse rotational axis A (FIG.4). As seen best in FIG. 8, the distal end of the femur rod 108 has afirst coupler (e.g., a fork coupler) hingedly couplable with a secondcoupler (e.g., a male coupler) at a proximal end of the tibia rod 110.In the illustrated embodiment, the first and second couplers definealigned transverse openings 112, 113, respectively, through which ahinge pin, generally indicated at 114 in FIG. 7, is inserted to allowrotational movement of the tibia rod 110 relative to the femur rod 108about the transverse rotational axis A. In one or more embodiments, thefemur rod 108 and the tibia rod 110 may be formed from, for example, oneor more of metal, PMMA (Poly(methyl methacrylate)) (e.g., coated withPMMA), polyethylene, other suitable materials, and combinations thereof.

The hinge pin 114 may be of suitable design and construction. In one ormore embodiments, such as shown in FIG. 7, the hinge pin 114 comprises acylindrical bearing 114 a having a first end shoulder or stop, and aretainer 114 b having a second end shoulder or stop. The cylindricalbearing 114 a is internally threaded to threadably mate with externalthreading on a shaft of the retainer 114 b to form the hinge pin 114.The end shoulders retain the hinge pin within the couplers of the femurand tibia rod 108, 110. In one or more embodiments, such as shown inFIGS. 9A and 9B, a hinge pin 114′ may include a cylindrical bearing 114a′ having an end shoulder or stop, and a snap-fit retainer 114 b′including cantilevered snap-fit arms and an end shoulder or stop. Thesnap-fit arms are slidably insertable into the cylindrical bearing 114a′ and secured therein by snap-fit connection, as shown in FIG. 9B, toform the hinge pin 114′. The end shoulders retain the hinge pin 114′within the couplers of the femur and tibia rods 108, 110. In one or moreembodiments, the hinge pin may be a hinge pin secured in the alignedopenings of the femur and tibia rods 108, 110 by a cotter pin orretaining ring, as is generally known. The femur and tibia rods 108, 110may be hingedly couplable to one another in other ways. For example, inFIG. 10 another hinged rod assembly 102′ comprises a femur rod 108′, anda tibia rod 110′ hingedly coupled to the femur rod at a hinged joint toallow rotational or pivoting motion of the tibia rod relative to thefemur rod about a transverse rotational axis A′. The hinged rod assembly102′ is similar to the hinged rod assembly 102 and functions, inoperation, in essentially the same way. The distal end of the femur rod108′ has a first coupler (e.g., a fork coupler) hingedly couplable witha second coupler (e.g., a male coupler) at a proximal end of the tibiarod 110′. In the illustrated embodiment, the first and second couplersdefine aligned transverse openings through which a hinge pin, generallyindicated at 114′, is inserted to allow rotational movement of the tibiarod 110′ relative to the femur rod 108′ about the transverse rotationalaxis A′. Compared to the hinged rod assembly 102, the fork coupler ofthe femur rod 108′ of the present hinged rod assembly 102′ has struts ortines that have a greater thickness than struts or tines of the otherhinged rod assembly 102. Moreover, the hinge pin 114′ in this embodimentmay comprise a single component having a snap-fit connector that “snaps”directly onto the distal end of the femur rod 108′, rather than atwo-piece component as shown in FIGS. 9A and 9B, for example.

Referring to FIGS. 13-15, the femur rod 108 is configured to be insertedinto the medullary canal of the femur. The tibia rod 110 is configuredto be inserted into the medullary canal of the tibia. As explained inmore detail below, when the femur and tibia rods 108, 110 are insertedinto the respective medullary canals of the femur and tibia, the axis ofthe hinged joint is located generally at the rotational axis of the kneeto allow at least limited extension and flexion of the knee. Moreover,the hinged rod assembly 102 (e.g., the hinge joint) may bear at leastsome of the load at the knee joint. The femur and tibia rods 108, 110may be constructed of suitable biocompatible material that is generallyrigid. For example, the rods 108, 110 may be formed from stainlesssteel, titanium, or other materials. In one or more embodiments, thebody or shaft of the femur rod 108 may have a diameter from about 10 mmto about 16 mm, or other suitable diameters or cross-sectionaldimensions. In one or more embodiments, the femur rod 108 may have alength from about 150 mm to about 200 mm, or other suitable lengths. Inone or more examples, the body or shaft of the tibia rod 110 may have adiameter from about 10 mm to about 14 mm, or other suitable diameters orcross-sectional dimensions. In one or more embodiments, the tibia rod110 may have a length of about 150 mm, or other suitable lengths.

Referring to FIGS. 4, 5 and 11A-12C, the articulating component assembly104 generally comprises a femoral spacer component 120 and a tibialspacer component 122. The femoral spacer component 120 is configured tobe secured to the distal end of the femur, such as by bone cement (e.g.,PMMA (Poly(methyl methacrylate))), which may be pre-loaded withantibiotics. The femoral spacer component 120 may be pre-formed (i.e.,pre-manufactured) from bone cement (e.g., PMMA) and impregnated withantibiotics (e.g., gentamicin), similar to conventional articulatingspacers. The femoral spacer component 120 may have a shape similar toconventional femoral articulating spacers and/or TKA femoral spacercomponents or may have other suitable shapes. The tibial spacercomponent 122 is configured to be secured to the proximal end of thetibia, such as by bone cement (e.g., PMMA), which may be pre-loaded withantibiotics. The tibial spacer component 122 may be pre-formed (i.e.,pre-manufactured) from bone cement (e.g., PMMA) and impregnated withantibiotics (e.g., gentamicin), similar to conventional tibialarticulating spacers. The tibial spacer component 122 may have a shapesimilar to conventional tibial articulating spacers and/or TKA tibialspacer components or may have other suitable shapes. When implanted,respective articular surfaces of the femoral and tibial spacercomponents 120, 122 engage one another through range of motion of theknee while bearing at least some load.

As shown in FIG. 11A-12C, unlike conventional articulating spacers, thefemoral and tibial spacer components 120, 122 define openings 120 a, 122a, e.g., through openings, recesses, or clearances, in or through whichthe hinged rod assembly 102 is received. In the illustrated embodiment,only the tibia rod 110 extends through the openings 120 a, 122 a suchthat the hinged joint of the hinged rod assembly 102 is superior to theopenings. In one or more other embodiments, the hinged joint of thehinged rod assembly 102 may be received in the openings 120 a, 122 asuch that the openings provide clearance for the hinged joint throughrange of motion of the knee. It is understood that the hinged joint ofthe hinged rod assembly 102 may be disposed at any location relative tothe openings 120 a, 122 a of the femoral and tibial spacer components120, 122 that is suitable for allowing at least some range of motion ofthe hinged rod assembly 102 and the knee joint. Another embodiment of afemoral spacer component is generally indicated at reference numeral120′. In this embodiment, the femoral spacer component 120′ defines anotch 120 a′ or recess extending from a posterior end of the component.This is slightly different than the through opening 120 a of the femoralspacer component 120. Other configurations of the opening 120 a, 120 a′are possible.

Referring to FIGS. 16A-16C, in one or more embodiments, the hingedarticulating spacer system 100 is utilized in a two-stage revision TKA.As shown in FIG. 16A, in a first step, the femoral and tibial TKAcomponents are removed from the patient. As is known, in general thejoint space is cleaned, and remaining bone cement and necrotic debrisand bone tissue is removed, leaving a large joint space between thefemur and tibia. Next, one or both of the femur rod 108 and the tibialrod 110 are individually inserted into the respective medullary canalsof the femur and tibia. That is, the femoral and tibial rods may beunattached when inserted into the respective bones. Bone cement may beused to secure the femoral and tibial rods 108, 110 to the respectivefemur and tibia. Other ways of fixing the rods to the respective bonesmay be used. For example, the rods may include friction-enhancingstructures, such as teeth or ribs or knurls, for increasing friction andinhibiting axial movement of the hinged rod assembly 102 within themedullary canals.

The femoral and tibial spacer components 120, 122 are inserted into thejoint space and after insertion of the femur and tibia rods 108, 110,respectively. For example, as shown in FIG. 16B, the femoral spacercomponent 120 may be placed on the distal end of the femur such that thefemur rod 108 is received in the opening 120 a of the femoral spacercomponent 120, and the tibial spacer component 122 may be placed on theproximal end of the tibia such that the tibia rod 110 is received in theopening 122 a of the tibial spacer component. Bone cement may be appliedto the respective ends of the femur and the tibia and/or of therespective surfaces of the femoral and tibial rods to facilitatecoupling of the components to the respective bones. In another example,the tibia rod 110 may be inserted through the openings 120 a, 122 a ofboth the tibial and femur components 122, 120, such as in an embodimentwhere the femur component is not inserted into the opening of the femur,such as shown in FIGS. 4 and 5.

With the rods 108, 110 in place and the femoral and tibial spacercomponents 120, 122 in the joint space, the femur and tibia rods arethen hingedly coupled to one another, such as by bringing the respectivecouplers together and inserting the hinge pin 114 through alignedtransverse openings 112, 113 in the couplers. At this time, thearticular surfaces of the femoral and tibial spacer components 120, 122may contact and engage one another. Bone cement 130 may be applied tobone defects in the femur and tibia. Moreover, additional bone cementmay be applied to facilitate proper seating and securement of thefemoral and tibial spacer components 120, 122 on the respective bones.

In the second stage of the revision TKA, the hinged articulating spacersystem 100 is removed, typically 6 to 12 weeks after implantation. Therevision TKA system is then implanted. Thus, the hinged articulatingspacer system 100 is only temporary and used to facilitate eradicationof the infection.

It is believed that the teachings set forth in the present disclosureprovide a hinged articulating spacer system that allows for range ofmotion of the knee joint while inhibiting dislocation of the jointduring the infection-treatment time of a two-stage revision TKA. Thus,it is believed the patient is more mobile and ambulatory, with reducedpain and risks of dislocation of knee joint, compared to both the staticspacer and the articulating spacer. This further leads to a betterquality of life for the patient and increases success of the secondstage of the revision TKA.

Modifications and variations of the disclosed embodiments are possiblewithout departing from the scope of the invention defined in theappended claims.

When introducing elements of the present invention or the embodiment(s)thereof, the articles “a”, “an”, “the” and “said” are intended to meanthat there are one or more of the elements. The terms “comprising”,“including” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

As various changes could be made in the above constructions, products,and methods without departing from the scope of the invention, it isintended that all matter contained in the above description and shown inthe accompanying drawings shall be interpreted as illustrative and notin a limiting sense.

What is claimed is:
 1. A hinged articulating spacer system for revisionknee arthroplasty comprising: a femur rod configured to be inserted intoa distal end of a femur; a tibia rod configured to be inserted into aproximal end of a tibia, wherein the tibia rod is configured to behingedly coupled to the femur rod to form a hinged rod assembly; apre-formed femoral spacer component including bone cement impregnatedwith an antibiotic, the pre-formed femoral spacer defining an openingconfigured to receive the hinged rod assembly; and a pre-formed tibialspacer component including bone cement impregnated with an antibiotic,the pre-formed tibial spacer defining an opening configured to receivethe hinged rod assembly.
 2. The hinged articulating spacer system setforth in claim 1, further comprising a hinge pin configured to hingedlycouple the femur and tibia rods to one another to form the hinged rodassembly.
 3. The hinged articulating spacer system set forth in claim 2,wherein the femur rod has a distal end defining an opening, wherein thetibia rod has a proximal end defining an opening, wherein the openingsof the femur rod and the tibia rod, respectively, are alignable and thehinge pin is receivable in the openings when the openings are aligned tohingedly couple the tibia rod to the femur rod.
 4. The hingedarticulating spacer system set forth in claim 3, wherein the hinge pinincludes a snap-fit connection.
 5. The hinged articulating spacer systemset forth in claim 3, wherein the distal end of the femur rod includes afork coupler defining the opening.
 6. The hinged articulating spacersystem set forth in claim 5, wherein the proximal end of the tibia rodis insertable between tines of the fork coupler.
 7. The hingedarticulating spacer system set forth in claim 1, wherein the femur rodhas distal end including a fork coupler.
 8. The hinged articulatingspacer system set forth in claim 7, wherein the tibia rod has a proximalend insertable between tines of the fork coupler.
 9. The hingedarticulating spacer system set forth in claim 1, wherein the femur rodand the tibia rod comprise one or more of metal, PMMA (Poly(methylmethacrylate), polyethylene, and combinations thereof.
 10. The hingedarticulating spacer system set forth in claim 1, wherein the cement ofthe pre-formed femoral spacer and the pre-formed tibial spacer comprisePMMA (Poly(methyl methacrylate).
 11. The hinged articulating spacersystem set forth in claim 1, wherein the antibiotic comprisesgentamicin.
 12. A method of performing a revision total kneearthroplasty, the method comprising: removing a total knee arthroplastyprosthesis from a knee joint of a patient, thereby creating a jointspace; inserting, after said removing the total knee arthroplastyprosthesis, a hinged articulating spacer system, wherein said insertinga hinged articulating spacer system includes inserting a femur rod of ahinged rod assembly into a distal end of a femur of the knee joint,inserting a tibia rod of the hinged rod assembly into a proximal end ofa tibia of the knee joint, inserting a pre-formed femoral spacercomponent into the joint space, inserting a pre-formed tibial spacercomponent into the joint space, and hingedly coupling the femur rod andthe tibia rod to one another to assemble the hinged rod assembly,wherein when assembled the hinged rod assembly extends through thepre-formed femoral and tibial spacer.
 13. The method of performing arevision total knee arthroplasty set forth in claim 12, wherein saidhingedly coupling the femur rod and the tibia rod to one anothercomprises inserting a hinge pin through the femur rod and the tibia rod.14. The method of performing a revision total knee arthroplasty setforth in claim 13, wherein said inserting a hinge pin through the femurrod and the tibia rod comprises inserting a hinge pin through alignedopenings in the femur rod and the tibia rod.
 15. The method ofperforming a revision total knee arthroplasty set forth in claim 14,wherein said hingedly coupling the femur rod and the tibia rod to oneanother further comprises snap-fitting the hinge pin to secure the hingepin to the femur rod and the tibia.
 16. The method of performing arevision total knee arthroplasty set forth in claim 14, wherein a distalend of the femur rod includes a fork coupler.
 17. The method ofperforming a revision total knee arthroplasty set forth in claim 16,wherein said hingedly coupling the femur rod and the tibia rod to oneanother further comprises inserting a proximal end of the tibia rodbetween tines of the fork coupler of the femur rod.
 18. The method ofperforming a revision total knee arthroplasty set forth in claim 12,wherein the femur rod and the tibia rod comprise one or more of metal,PMMA (Poly(methyl methacrylate), polyethylene, and combinations thereof.19. The method of performing a revision total knee arthroplasty setforth in claim 12, wherein the pre-formed femoral spacer and thepre-formed tibial spacer comprise PMMA (Poly(methyl methacrylate). 20.The hinged articulating spacer system set forth in claim 1, wherein theantibiotic comprises gentamicin.